[Effects of wrist dorsiflexion and palmar flexion on median nerve displacement and cross-sectional area in patients with carpal tunnel syndrome].

Abstract

Objective: To evaluate the effects of wrist dorsiflexion/palmar flexion on median nerve displacement and cross-sectional area in patients with carpal tunnel syndrome.

Methods: From November 2019 to December 2021, a total of 85 patients (110 affected wrists) diagnosed with carpal tunnel syndrome (CTS) in our department were enrolled, including 15 males and 70 females, with an age range of 24 to 78 years old with a mean of (51.04±8.37 ) years old. According to the severity of the condition, the wrists were classified into a mild group (38 wrists), a moderate group (30 wrists), and a severe group (42 wrists). During the same period, 25 healthy controls were recruited, comprising 50 healthy wrists. All patients and healthy volunteers underwent high-frequency ultrasound examination to measure the vertical displacement of the median nerve relative to the transverse carpal ligament during wrist dorsiflexion/palmar flexion, as well as the changes in the cross-sectional area (CSA) of the median nerve at the pisiform level. All CTS patients also underwent electrophysiological testing to measure the sensory conduction velocity (SCV), sensory latency, and sensory nerve action potential (SNAP) amplitude of the median nerve.

Results: In the carpal tunnel syndrome (CTS) group, the distance from the proximal end of the median nerve to the transverse carpal ligament [2.59(2.24, 2.79) mm], the distance from the distal end to the transverse carpal ligament [2.11 (1.82, 2.31) mm], and the cross-sectional area[ 0.16(0.12, 0.19) cm²] during palmar flexion were all significantly lower than those during wrist dorsiflexion [2.62(2.27, 2.82) mm, 2.14(1.85, 2.34) mm, and 0.18(0.14, 0.21) cm², respectively (P<0.01)]. Similarly, in the control group, the distance from the proximal end of the median nerve to the transverse carpal ligament [2.88(2.54, 3.38) mm], the distance from the distal end to the transverse carpal ligament[2.33(1.99, 2.75) mm], and the cross-sectional area [0.06(0.02, 0.09) cm²] during palmar flexion were all significantly lower than those during wrist dorsiflexion[2.94(2.60, 3.44) mm, 2.39(2.05, 2.84) mm, and 0.10(0.07, 0.12) cm², respectively (P<0.01)]. Overall, there were statistically significant differences in the vertical distances from the proximal and distal ends of the median nerve to the transverse carpal ligament, as well as in the cross-sectional area, among the mild, moderate, severe, and control groups(P<0.01). The vertical distances from the proximal and distal ends of the median nerve to the transverse carpal ligament showed a significant positive correlation with sensory latency (r=0.468, 0.430, P<0.01) and a significant negative correlation with sensory conduction velocity(r=-0.449, -0.449, P<0.01).

Conclusion: Wrist dorsiflexion and palmar flexion significantly affect the displacement and cross-sectional area of the median nerve in patients with CTS. High-frequency ultrasonography is an effective tool for detecting these changes and assessing the severity of CTS, warranting its clinical application.